This invention relates to a tensioning device for a band, particularly a band made of plastic material such as postal strapping and the like.
Tensioning devices of this type known in the prior art have a rotary tensioning wheel which cooperates with an abutment plate which is pivotable relative to the tensioning wheel by a lever. Thus at least one of the two end portions of a band can be pressed against the tensioning wheel, which frictionally engages that end and draws it along the surface of the abutment plate, thus tensioning it. The lever has a handle at one end and the abutment plate at the other. By depressing the handle, the lever can be pivoted so that the abutment moves away from the tensioning wheel and band ends located between them are exposed and can be extracted.
In order to obtain a sufficiently high contact pressure during tensioning, the wedge angle between the tensioning wheel and the pivot axis of the lever is made as small as possible. Then, when the high band tension which is necessary of securing a band around a parcel is attained, there are extremely high forces between the abutment plate and the tensioning wheel, so that it is difficult to move the handle of the lever to release the abutment plate from the band ends clamped between it and the tensioning wheel.